Apparatus for making a multi-layer injection blow molded container

ABSTRACT

Apparatus for making a rigid container by injection molding a parison having plural layers of polymers. The parison is blow molded to the final shape of the container. Control during injection is exercised over each of the plural polymers so as to produce uninterrupted layers extending throughout the walls of the parison and to insure that the interior layers are completely encapsulated within the outer layers.

This is a continuation of application Ser. No. 059,375, filed July 20,1979 now abandoned.

BACKGROUND OF THE INVENTION

Food product rigid containers generally must be impermeable to oxygen.Most common structural polymers for rigid food containers are permeableto oxygen which invades the food product causing degradation orspoilage. Those polymers which are sufficiently impermeable to oxygengenerally are not suitable alone for rigid containers for foods becausethey do not possess adequate structural properties, are moisturesensitive, or are not approved for or are of questionable safety whenused in contact with foods. Ethylene vinyl alcohol copolymer (EVOH) is atransparent extrusible material possessing high impermeability to oxygenwhen dry, many times less permeable than acrylonitrile copolymers, butis very moisture sensitive. The oxygen barrier properties of EVOH aremarkedly diminished in the presence of significant quantities of water.To be useful for food packaging, particularly where extended shelf lifeis required, EVOH must be kept dry as by total encapsulation withinpolymers which have good moisture barrier properties.

Many foods are processed in the container in a pressure cooker orretort. Retort conditions commonly are 250° F. at 30 psia steampressure. A rigid container must survive retort conditions. It must notpermanently distort during cooking or during cooling, and must notsuffer an alteration of the desirable properties of its components.Polyolefins, particularly blends or copolymers of polypropylene andpolyethylene, are well suited to manufacture of rigid containers andhave adequate physical properties to survive retorting. Polyolefins arerelatively poor oxygen barriers, but are relatively good moisturebarriers. The use of polyolefins with a central core of an oxygenbarrier polymer is a desired goal of the food packaging industry.

Nohara et al. U.S. Pat. No. 3,882,259 discloses a three ply plasticbottle having a core of EVOH blended with Surlyn A brand ionomer resinand outer plies of polyethylene blended with Surlyn A. The Surlyn Aionomer is added to both the EVOH and the polyethylene resin materialsto improve adhesion between layers. The bottle is to be made byextrusion blow molding whereby the three layers are simultaneouslyextruded to produce a three ply tube. While still hot from extrusion,the tube is pinched together at the bottom to form a seal and inflatedin a blow mold having the shape of the desired bottle.

Extrusion blow molding has four serious drawbacks when used to formmulti-layer containers having a core ply of a moisture sensitive barriermaterial such as EVOH.

First, the pinch seal at the bottom leaves the core ply of EVOH exposedon the bottle exterior. Since EVOH and certain other barrier materialsare adversely affected by moisture, exposure of the core ply at thecontainer bottom renders the container susceptible to loss of barrierquality by intrusion of moisture. The risk that the container exteriorwill encounter damp conditions in storage or transport is high and theresulting loss of barrier quality will degrade or spoil the food.Further, retort conditions are such that moisture from the steam willintrude into the barrier layer through the exposed barrier at thebottom.

Second, extrusion blow molding necessarily produces scrap as a result ofthe pinch sealing procedure. Since the scrap contains materials fromeach of the three layers, re-extrusion of the scrap is difficult andexpensive.

Third, the pinch seal produces a bottom of non-uniform thickness andstrength. The sealing takes place along a line between the abuttingfaces of the inner layer material. The seal line is bordered by regionsof relatively thick material. When stretched during blow molding, thebottom varies in thickness in the vicinity of the pinch seal. Because ofthe thickness variation due to the pinch seal, the stiffness of thebottom is not uniform along all diameters. Consequently, the bottom doesnot evenly respond to expansion and contraction as the product changesin temperature. This lack of even response causes unpredictableperformance of the container when retorted.

Fourth, the pinch seal may create an interruption in the barrier layer.If the inside surface layer is interposed between the barrier layer atthe seal, a line lacking barrier material will result. The area of theinterruption may be great enough to allow sufficient oxygen to enter tobe a problem.

Because of these disadvantages, extrusion blow molding cannot produce anentirely satisfactory three layer rigid container having a core barrierlayer of a moisture sensitive polymer such as EVOH, particularly wherethe container is intended for retorting.

SUMMARY OF THE PRESENT INVENTION

The present invention is concerned with apparatus for making a plasticcontainer by injection molding or by an injection blow molding techniquewhich produces a container whose walls are multiple plies of differentpolymers. In particular, the container walls comprise inner and outerlayers of structural polymers such as polyolefins or a blend ofpolyolefins on either side of a core layer of a polymer having oxygenbarrier properties such as EVOH.

Injection blow molding is a process whereby a preform or parison isformed by injection molding in a cavity. The parison is transferred to ablow mold cavity and blown to the shape of the desired container. Theparison can be retained on the core pin of the injection mold andtransferred on the core pin to the blow molding cavity. The parison canbe temperature conditioned before blow molding to achieve an optimumtemperature or profile of temperatures. The core pin can be temperaturecontrolled and the exterior of the parison can be temperatureconditioned by contact with air or other fluid such that blow moldingoccurs at optimal conditions. Orientation can be achieved as the parisonis stretched during blow molding. Injection blow molding produces noscrap and requires no pinch seal.

According to the present invention, polymer melts for the inside andoutside surface layers and the core layer of the container walls aresubstantially simultaneously injected into a parison mold cavity throughan injection nozzle having separate passages for each polymer meltarranged to lead to coaxial annular nozzle orifices surrounding thecentral orifice. Additional layers or layers interposed between thesurface and core layers can also be injected simultaneously to produce acontainer wall having four or more layers.

The initiation, rate, and termination of flow for each layer areindependently and continously controlled to provide control over thethickness of each layer and to insure that the core layer or layers aretotally encapsulated between the surface layers. The injection moldedparison is transferred on the core pin to a blow mold cavity having theshape of the container and is then blow molded into the finishedcontainer. Temperature conditioning of the parison just prior to blowingcan result in biaxial orientation of the various polymers to achievedesirable improvements in physical properties such as impermeability,clarity, tensile strength, impact strength, and resistance to creep. Theresulting product has a barrier layer or layers which extend withoutinterruption throughout the container, yet are completely encapsulatedwithin the material of the inside and outside surface layers. Since thebarrier layer is protected from moisture by the moisture barrierproperties of the surface layers, the oxygen barrier quality ispreserved.

DESCRIPTION OF A PREFERRED EMBODIMENT DRAWINGS

In the drawings:

FIG. 1 is a schematic view in cross-section of injection blow moldingapparatus,

FIG. 2 is a schematic view of the apparatus of the present invention,

FIG. 3 is a simplified view of the injection apparatus of the presentinvention,

FIG. 4 is a schematic view illustrating the control system for one ofthe injection rams,

FIG. 5 is a plot of the position of one of the injection rams as afunction of time,

FIG. 6 is a flow chart for the control system for the apparatus,

FIG. 7 is a plot of ram position as a function of time for three rams,

FIGS. 8-15 are views in cross-section taken through the nozzle andcavity showing the confluence of flow of the various layers at varioustimes during the injection cycle,

FIG. 16 is a view in cross-section of the injection nozzle,

FIG. 17 is a view in cross-section of the parison, FIG. 18 is a view incross-section of the finished container,

FIG. 19 is an enlarged view of a portion of a container wall havingthree layers,

FIG. 20 is a plot of the oxygen permeability of a barrier material as afunction of moisture content, and

FIG. 21 is an enlarged view of a portion of a container wall having fivelayers.

The machine of the present invention injection molds a multi-layerparison from a plurality of polymers, each separately plasticated andfed to separate injection rams. The rams each force a shot of polymer toappropriate nozzle passages which lead to the entrance to the injectionmold cavity. Conditions are controlled to advance the several polymermelts substantially simultaneously in the die cavity under non-turbulentflow conditions to preserve the polymers as discrete layers in theparison. The following detailed description explains how the foregoingis accomplished.

FIG. 1 shows a portion of the injection blow molding machine (IBM) ofthe present invention. Two core pins 10A, 10B are mounted on atransversely moveable plate 40 on the axially moveable platen 42 of themachine. Core pin 10A is positioned in an injection mold 20 while corepin 10B is positioned in a blow mold 30B. When plate 40 is traversed tothe left, core pin 10A will be in blow mold 30A and core pin 10B will bein the injection mold 20. A parison is removed from the mold by axialretreat of the moveable platen 42 and the plate 40 with core pins 10 istraversed either left or right to the available blow mold. FIG. 1 showsblow mold 30A ready to receive the parison and shows blow mold 30Bcontaining a parison 60B. Parison 60B is inflated with air to assume theshape of blow molding cavity 30B while parison 60A is being injected incavity 20. The blow molds open as the platen retreats to eject thefinished container. The plate 40 shuttles back and forth each cycle sothat a container is blown simultaneously each time a parison isinjected.

FIG. 2 shows the general layout of the injection blow molding machineand indicates the control means. Plasticators 82A, 82B, 82C feed threerams 70A, 70B, 70C for three polymer melts which are fed to a manifoldblock 75 which contains separate passages leading to a multi-passagenozzle 50 for the injection mold 20. The platen 42 is moved axially ofthe mold by a hydraulic press 44. Control circuitry means for the pressand blowing cycles are indicated at press control block 110. Amicroprocessor 100 is programmed to control the servo hydraulics 120which control the individual injection rams and to command the presscontrol block 110.

FIG. 3 shows one of the plural plasticators 82B for melting andsupplying molten polymer B to an injection ram 70B. The plasticator 82Bis a conventional reciprocating screw device which forces molten polymerinto the cylinder 71B of the ram when manifold valve 84B is closed andmanifold valve 85B is opened and the ram is retreated to the left byhydraulic actuator 72B. When the ram cylinder 71B is charged with moltenresin, valve 85B is closed. Upon a control signal from themicroprocessor 100, valve 84B is opened and the servo control 120 forthe ram causes the ram to advance to the right, according to adisplacement-time schedule stored in the microprocessor program. Adisplacement transducer 76 provides an analog signal proportional to ramdisplacement to complete a feed-back loop for the servo 120. Polymer Bforced according to the program flows past valve 84B through themanifold passages to the injection nozzle, through the nozzle passagesand into the injection mold cavity where polymer B becomes the outerlayer of a parison 60.

FIG. 4 shows schematically the servo loop where the control signal fromthe microprocessor 100 (shown as voltage as a function of time) and aposition signal from the displacement transducer 76 are algebraicallycombined in an amplifier 78 and the resulting signal is used to controlthe hydraulic servo 120 for the hydraulic actuator 72. A typical ramposition control signal is shown in FIG. 5. Since displacement ismeasured by transducer 76, the plot is in voltage as a function of time.

FIG. 6 is a flow chart of the system used to control the machine. Theinjection blow molding machine is indicated as IBM on the chart. Uponinitiation of the cycle, the program checks positions of valves, rams,etc. and if all are proper, recharges the ram cylinders 71 from theplasticators 82. The IBM control circuit 110 provides an "inject" signalto the microprocessor 100. Injection is carried out according to the ramdisplacement-time schedule of the microprocessor and is terminated atthe end of the schedule. An "injection complete" signal is sent to theIBM. The control 110 then causes the IBM to traverse to place theparison in the blow mold and to procede with the blow molding phase. Themachine continues to cycle through this sequence. Keyboard 115 may beused to change the displacement-time schedule or to shut down themachine.

FIG. 7 is a plot of ram displacement as a function of time for threerams. The positions of the rams are measured as the voltage analogoutput of the transducers 76 for each ram. The polymer for the insidesurface layer is "A"; that for the core layer "C"; and that for theoutside surface layer is "B". In this figure an upward slope indicates aforward motion of the ram to deliver polymer, a horizontal slopeindicates a stopped ram, and a downward slope indicates a retreat of theram. The significance of FIG. 7 is perhaps better understood byreference to FIGS. 8-15, which show the flow of the polymers at the exitof the nozzle 50 and the entrance 52 of the injection mold cavity 20 atthe rounded bottom of the parison. FIGS. 8-15 are taken at differenttimes in the cycle and those times are keyed to FIG. 7.

FIG. 8 represents the conditions at the start of a cycle at time 0. Thecavity 20 is empty. The entrance 52 of the cavity 20 initially containsonly the polymers A and B for the inside and outside surface layers. Therams for polymers A and B begin to advance to force those polymers intothe cavity. At about 100 milliseconds into the cycle the ram for thecore layer, polymer C, begins to advance. FIG. 9 shows that polymer Chas joined the flow stream in the entrance and polymer C is about toenter the cavity. FIG. 10, taken at about 520 milliseconds, shows theflow of the three polymers as the cavity continues to be filled. Allthree polymer layers must extend throughout the entire length of theparison. Since the flow in the mold cavity is laminar, the velocity inthe middle of the stream is higher than the velocities at the cavitywalls. Therefore, initiation of flow of polymer C is retarded enough(e.g., about 100 milliseconds) so that polymer C will reach the far endof the cavity just as the slower moving surface layers (A and B) reachthe end. In this way, the far end of the parison, that which becomes themouth end of the container, will have all layers present in their properpositions.

At about 1000 milliseconds into the injection cycle, the ram for polymerA (the inside surface layer) is stopped and the ram for polymer C (thecore layer) can be accelerated slightly to achieve the desired thicknessof material in the bottom of the container. Polymer A is necked down inthe entrance 52 as is shown in FIG. 11 until it effectively is severedas shown in FIG. 12. At 110 milliseconds the ram for polymer C isstopped and the ram for polymer A is restarted. FIGS. 13 and 14 showpolymer A advancing to pinch off polymer C in the entrance, therebypushing the last of polymer C into the cavity 20 with polymer A to buryor encapsulate to isolate polymer C from exposure at the surface of theparison. FIG. 15 shows polymer A knit to polymer B at the entrance tocomplete the encapsulation of polymer C and to return to the conditionsat the start as shown in FIG. 8. At the time of FIG. 15 (1300milliseconds) all three rams are retreated to depressurize the cavity toprevent expansion of the parison when the cavity is opened and todepressurize the polymers remaining in the nozzle and entrance toprevent exudation from the nozzle while the cavity is open. Thisexudation leads to premature flow of polymers into the cavity during thenext cycle which can lead to smearing of polymer C on the surfaces ofthe container.

1500 milliseconds marks the end of the injection phase of the machinecycle for this example. Subsequent to the end of the injection phase ofthe cycle, manifold valves 84, 85 are actuated and the ram cylinders 71are recharged with their polymers by the plasticators 82. The injectionmold is opened by retreating the hydraulic press 44 to withdraw the corepin 10 from the cavity 20. The parison just formed is transferred to oneof the blow mold cavities 30A, 30B and the container which was blowmolded simultaneously with the injection cycle is ejected from the blowmold in which it was finished.

FIG. 16 shows a nozzle 50 appropriate for injection of a parison havinga three layer wall. Polymer B, which forms the outside surface layer, isdelivered by the ram 70B to an annular exit distribution channel 54Bwhich distributes the polymer circumferentially of the nozzle structure.Polymer B advances along a conical passage 56B to an annular exitorifice 58B at the exit of the nozzle which leads to the injectioncavity. Similarly, polymer C, which forms the core layer, is deliveredby ram 70C to annular distribution channel 54C and thence along conicalpassage 56C to annular orifice 58C. Polymer A, which forms the insidesurface layer, is delivered by the ram 70A to a passage 56A which exitsthrough an exit orifice into the center of the concentric flows issuingfrom orifices 58B and 58C. A nozzle shut off valve 59 can be movedaxially to arrest flow of polymer A.

FIGS. 17 and 18 compare the parison 60 as injection molded with thefinished container. The neck portion 62 remains virtually unchangedduring blow molding. The parison is held by the chilled neck portionwhile the hot and soft parison is blown. Thus, the neck 62 including theflange 64 is essentially formed in the injection mold. The remainder ofthe parison walls including the wall which forms the parison's bottomportion 61 which in turn forms the parison's closed end 63 are thinnedas the parison is stretched during blow molding.

FIG. 18 shows that the core layer C extends throughout the flange 64,but does not penetrate the flange edge. This is accomplished in largepart by selection of the delay time in starting the ram for the corepolymer. The flange 64 will be employed in a double seam seal when ametal end is crimped, by well known techniques, onto the container mouthto close the filled container. Since the flange represents a significantarea, it is important that the core layer extend well into the flange.The programmed flows of the various polymers also ensure that the corelayer is not exposed at the sprue mark at the central exterior of thecontainer.

FIG. 19 is an enlargement of the container wall within the circle ofFIG. 18. Layer A is the inside surface layer formed from polymer A inthe foregoing description. Layer B is the outside surface layer, formedfrom polymer B. Layer C is the core or barrier layer formed from polymerC. The thinnest layer is the relatively expensive barrier polymer C. Therelative thickness of the three layers is controlled by controlling therelative flow rates of the three polymers by microprocessor control ofthe displacement rates of the rams. A preferred wall structure is alayer of a blend of high density polyethylene and polypropylene on eachface of a core barrier layer of ethylene vinyl alcohol copolymer (EVOH).

FIG. 20 shows how the oxygen barrier quality of EVOH decreases abruptlyat high levels of moisture. Where the EVOH layer is thin, only a smallquantity of water will cause a large increase in oxygen permeability.For this reason, the EVOH layer must adequately be protected against theintrusion of moisture.

Polyolefins do not adhere well to EVOH. Adhesion can be improved byadding adhesion promotors to the polyolefin, the EVOH or both. Anotherapproach is to provide an intermediate layer of an adherent polymericmaterial which adheres to the polyolefin and the EVOH. Such materialsinclude modified polyolefins sold under the name Plexar by the ChemplexCompany of Rolling Meadows, Ill. These comprise a blend of a polyolefinand a graft copolymer of high density polyethylene and an unsaturatedfused ring carboxylic acid anhydride. The polyolefin component of theblend can be polyethylene or preferably is an olefin copolymer such asethylene vinyl acetate. Schroeder application Ser. No. 973,943 filedDec. 28, 1978 U.S. Pat. No. 4,254,169 teaches the use of these materialsto bond to EVOH. The materials themselves are disclosed in U.S. Pat.Nos. 4,087,587 and 4,087,588. We have found these modified polyolefinsto be suitable as interlayers to improve adhesion between the polyolefinsurface layers and the EVOH core layer.

Another suitable material for use as an interlayer to improve adhesionbetween the EVOH polyolefins are maleic anhydride grafted polyolefinssold under the name Admer by Mitsui Petrochemical Industries of Tokyo,Japan.

The use of interlayers on each side of the EVOH oxygen barrier layerresults in a five layer container. To produce such a container, thethree passage nozzle of FIG. 16 is replaced with a five passage nozzleof similar construction. Where the inside and outside surface layers areof the same polymer one ram can be used for both those layers. The flowfrom that ram is divided and proportioned with part supplying thecentral axial passageway to form the inside surface layer and thebalance supplying the outermost nozzle annular orifice. The twoadditional nozzle orifices are located just inside and just outside thenozzle orifice for the EVOH barrier layer. The two additional annularnozzle orifices can be supplied with the interlayer polymer from asingle ram, the flow being divided and proportioned. Thus, a three rammachine can produce a five layer parison. Greater control can beexercised over the polymer flows by using a machine with anindependently controllable ram for each layer. A nozzle shut off valvecan be employed to selectively control the polymer flows. The threelayers of interlayer polymer and the barrier polymer can be treated as asingle core layer. A five layer wall is shown in FIG. 21 wherein layersA and B are the inside and outside surface layers of polyolefin, layer Cis the barrier layer of EVOH, and two layers D are the interlayermaterial.

EXAMPLE I

Five layer containers having a capacity of about 51/2 ounces, of 202×307size, weighing about 11 g were made using a five orifice nozzle on athree ram machine. The inside and outside surface layers werepolypropylenepolyethylene block copolymer (Hercules Profax 7631). Theadhesive interlayers were ethylene vinyl acetate copolymer blended witha graft copolymer of high density polyethylene and a fused ringcarboxylic acid anhydride (Plexar 1615-2). The oxygen barrier was EVOH(Kuraray EVAL EP-F, available from Kuraray Co. Ltd., Osaka, Japan). Thelayers were well adhered. The barrier extended to the flange lip and wascompletely encapsulated.

EXAMPLE II

Five layer containers similar to those of Example I were made whereinthe inside and outside surface layers were polypropylene (EXXON E612);the interlayer material was Plexar III, a blend of ethylene vinylacetate copolymer and a graft copolymer; and the barrier was EVAL EP-F.The layers were well adhered. The barrier layer extended to the lip ofthe flange and was completely encapsulated.

EXAMPLE III

Five layer containers similar to those of Example I were made whereinthe inside and outside surface layers were a 50--50 blend ofpolypropylene (EXXON E612) and high density polyethylene (Chemplex5701); the interlayer material was Plexar III; and the barrier layer wasEVAL EP-F. The layers were well adhered. The barrier layer extended tothe lip of the flange and was completely encapsulated.

EXAMPLE IV

Five layer containers similar to those of Example I were made whereinthe inside and outside surface layers were a copolymer of propylene andethylene (Hercules Profax 7631); the interlayer material was maleicanhydride grafted polyolefin (mitsui Admer QB 530); and the barrierlayer was EVAL EP-F. The layers were well adhered. The barrier layerextended to the lip of the flange and was completely encapsulated.

In the making of the containers of Examples I-IV the injection schedulebegan feeding the inside and outside surface layer polymer than thepolymer for the adhesive interlayer was started and substantiallysimultaneously the barrier layer polymer was started. The flows of theadhesive interlayer polymer and the barrier layer polymer wereterminated before the outside surface layer polymer flow was terminated.

I claim:
 1. Apparatus for making a multi-layer rigid article,comprising:(A) an injection mold and a core pin which together define acavity for molding a parison having a bottom portion, the cavity havingan entrance at the bottom portion of the parison,(1) an injection nozzlehaving an exit communicative with the entrance, a flow path for each ofthree polymer streams, and exit orifices for the polymer streamscommunicative with said nozzle exit, (2) means for independentlycommencing in the nozzle exit the flow of a first polymer stream tobecome the inside surface layer of the parison and the flow of a secondpolymer stream to become the outside surface layer of the parison, andthe flow of a third polymer stream between the first and second polymerstreams to become an inner layer of the parison, (3) means forindependently controlling the flow of each of the three polymer streamsrelative to each other during each injection cycle, (4) means forindependently terminating the flow of each of the polymer streams,operable to terminate each or any of said polymer streams independentlyof one another and at predetermined including differing times duringeach injection cycle, (5) means associated with the independentcommencing means, the independent controlling means and the independentterminating means, for coordinating their respective functions in apredetermined manner during the injection cycle, to permit terminationof the flow of the first polymer stream, then termination of the flow ofthe third polymer stream, and thereafter termination of the flow of thesecond polymer stream, to thereby enable the apparatus to provide thearticle with an inner layer formed from the third polymer stream that iscontinuous and is completely encapsulated within the surface layers, (b)means for transferring the injection molded parison to a blow moldingcavity having the configuration of the article, (C) means for inflatingthe parison in the blow molding cavity to form the article.
 2. Theapparatus of claim 1 including means for introducing a fourth polymerstream between the third and first polymer streams and means forintroducing a fifth polymer stream between the third and second polymerstreams, and means for controlling and for terminating the flows of thefourth and fifth polymer streams.
 3. Apparatus for making a multi-layerrigid container, comprising:(A) an injection mold and a core pin whichtogether define a cavity for molding a parison having a closed end, thecavity having an entrance for polymer at the closed end of theparison,(1) an injection nozzle having an exit communicative with theentrance, a flow path for each of three polymer streams, and exitorifices for the polymer streams communicative with said nozzle exit,(2) means for establishing in the entrance a flow of polymer comprisinga central stream of a first polymer surrounded by an annular stream of asecond polymer, (3) means for establishing an annular stream of a thirdpolymer between the first and second polymer streams, the third polymerstream being for forming an inner layer of the parison, (4) means forindependently controlling the flow of each of the three polymer streamsuntil the cavity is nearly filled during the injection cycle, (5) meansfor independently terminating the flow of each of the polymer streams,(6) means associated with the establishing means and with theindependent controlling means and the independent terminating means forcoordinating their respective functions in a predetermined manner duringthe injection cycle, to permit termination of the flow of the firstpolymer stream, then termination of the flow of the third polymerstream, and then termination of the flow of the second polymer stream,to thereby enable the apparatus to provide the parison with an innerlayer formed from the third polymer stream that is continuous and iscompletely encapsulated within surface layers formed from the firstpolymer stream and the second polymer stream, (B) means for transferringthe parison to a blow mold cavity, (C) means for inflating the parisonin the blow mold cavity to blow mold the parison into the finishedcontainer.
 4. Apparatus for injection blow molding a multi-layer rigidcontainer, comprising:an injection mold for a parison having a bottomportion, two core pins mounted on a plate which transverses to registereither pin with the injection mold, two blow molds for blow molding theparisons into the container, the blow molds being located to registerone blow mold with one core pin when the other core pin is registeredwith the injection mold, an injection nozzle in communication with theinjection mold at the bottom portion of the parison, the nozzle havingthree concentric exit orifices for three polymer streams communicativewith said nozzle exit, said three streams including a first stream tobecome the inside surface layer of the parison, a second stream tobecome the outside surface layer of the parison, and a third streambetween the two to become the inner layer of the parison, a plurality ofpolymer injection means associated with the nozzle orifices, controlmeans to independently control the flow of each of the polymer streamsas a function of time during the injection cycle, and to permit theindependent termination of flows of each of the polymer streams, andmeans associated with the control means for coordinating the flow andtermination of flow of each of the polymer streams as a function of timeduring the injection cycle, to permit termination of the flow of thefirst polymer stream, then termination of the flow of the third polymerstream, and thereafter termination of the flow of the second polymerstream, to thereby enable the apparatus to provide the parison andresulting container with an inner layer that is continuous and iscompletely encapsulated within the surface layers.
 5. The apparatus ofclaim 4 wherein the plurality of injection means comprises a pluralityof injection rams and a plurality of plasticators for supplying moltenpolymer to the injection rams, and wherein the control means control thedisplacement of the injection rams.
 6. Apparatus for making amulti-layer rigid article, comprising:(A) an injection mold and a corepin which together define a cavity for molding a parison having a bottomportion, the cavity having an entrance at the bottom portion of theparison,(1) an injection nozzle having an exit communicative with theentrance, a flow path for each of three polymer streams, and exitorifices for the polymer streams communicative with said nozzle exit,(2) means for independently commencing in the nozzle exit the flow of afirst polymer stream to become the inside surface layer of the parisonand the flow of a second polymer stream to become the outside surfacelayer of the parison, and the flow of a third polymer stream between thefirst and second polymer streams, to become an inner layer of theparison, said means for independently commencing the flows of thepolymer streams being operable independently of each other atpredetermined including differing times during the injection cycle, (3)means for independently controlling the rate of flow of each of thethree polymer streams relative to each other during each injectioncycle, to permit controlling and varying the relative thicknesses of therespective layers of and controlling and varying the location andthickness of the inner layer of the parison during the injection cycle,(4) means for independently terminating the flow of each of the polymerstreams, operable to terminate each or any of said polymer streamsindependently of one another and at predetermined including differingtimes during each injection cycle, (5) means associated with theindependent commencing means, the independent controlling means and theindependent terminating means for coordinating their respectivefunctions in a predetermined manner during the injection cycle, topermit termination of the flow of the first polymer stream, thentermination of the flow of the third polymer stream, and thereaftertermination of the flow of the second polymer stream to thereby enablethe apparatus to provide the article with an inner layer formed from thethird polymer stream that is continuous and is completely encapsulatedwithin the surface layers, (B) means for transferring the injectionmolded parison to a blow molding cavity having the configuration of thearticle, (C) means for inflating the parison in the blow molding cavityto form the article.
 7. Apparatus for making a multi-layer rigidcontainer, comprising:(A) an injection mold and a core pin whichtogether define a cavity for molding a parison having a closed end, thecavity having an entrance for polymer at the closed end of theparison,(1) an injection nozzle having an exit communicative with theentrance, a flow path for each of three polymer streams, and exitorifices for the polymer streams communicative with said nozzle exit,(2) means for establishing in the entrance a flow of polymer comprisinga central stream of a first polymer surrounded by an annular stream of asecond polymer, (3) means for establishing an annular stream of a thirdpolymer between the first and second polymer streams, (4) means forindependently controlling the rate of flow of each of the three polymerstreams until the cavity is nearly filled during the injection cycle, topermit controlling and varying the relative thicknesses of therespective layers of and controlling and varying the location andthickness of the inner layer of the parison during the injection cycle,(5) means for independently terminating the flow of each of the polymerstreams, (6) means associated with the establishing means and with theindependent controlling means and the independent terminating means forcoordinating their respective functions during the injection cycle, topermit termination of the flow of the first polymer stream, thentermination of the flow of the third polymer stream, and thentermination of the flow of the second polymer stream, to thereby enablethe apparatus to provide the parison with an inner layer formed from thethird polymer stream that is continuous and is completely encapsulatedwithin surface layers formed from the first polymer stream and thesecond polymer stream, (B) means for transferring the parison to a blowmold cavity, (C) means for inflating the parison in the blow mold cavityto blow mold the parison into the finished container.
 8. Apparatus formaking an at least five layered rigid article, comprising:(A) aninjection mold and a core pin which together define a cavity for moldinga parison having a bottom portion, the cavity having an entrance at thebottom portion of the parison,(1) an injection nozzle having an exitcommunicative with the entrance, a flow path for each of five polymerstreams, and exit orifices for the polymer streams communicative withsaid nozzle exit, (2) means for independently commencing in the nozzleexit the flow of a first polymer stream to become the inside surfacelayer of the parison, and the flow of a second polymer stream to becomethe outside surface layer of the parison, and the flow of a thirdpolymer stream between the first and second polymer streams to become aninner layer of the parison, and the flow of a fourth polymer streambetween the first and third polymer streams, and the flow of a fifthpolymer stream between the second and third polymer streams, (3) meansfor independently controlling the flow of each of the five polymerstreams relative to each other during each injection cycle, (4) meansfor independently terminating the flow of each of the polymer streams,(5) means associated with the independent commencing means, theindependent controlling means and the independent terminating means forcoordinating their respective functions in a predetermined manner duringthe injection cycle, to permit termination of the flow of the firstpolymer stream, then termination of the flow of the fourth and the thirdpolymer streams, and thereafter termination of the flow of the fifth andthe second polymer streams, to thereby enable the apparatus to providethe parison with an inner layer formed from the third polymer streamthat is continuous and completely encapsulated within the surfacelayers, (b) means for transferring the injection molded parison to ablow molding cavity having the configuration of the article, (C) meansfor inflating the parison in the blow molding cavity to form thearticle.
 9. Apparatus for making an at least five-layered rigidcontainer, comprising:(A) an injection mold and a core pin whichtogether define a cavity for molding a parison having a closed end, thecavity having an entrance for polymer at the closed end of theparison,(1) an injection nozzle having an exit communicative with theentrance, a flow path for each of five polymer streams, and exitorifices for the polymer streams communicative with said nozzle exit,(2) means for establishing in the entrance a flow of polymer comprisinga central stream of a first polymer surrounded by an annular stream of asecond polymer, (3) means for establishing an annular stream of a thirdpolymer between the first and second polymer streams, the third polymerstream being for forming an inner layer of the parison, means forestablishing a fourth polymer stream between the first and third polymerstreams, and means for establishing a fifth polymer stream between thesecond and third polymer streams, (4) means for independentlycontrolling the flow of each of the five polymer streams until thecavity is nearly filled during the injection cycle, (5) means forindependently terminating the flow of each of the polymer streams, (6)means associated with the establishing means and with the independentcontrolling means and the independent terminating means for coordinatingtheir respective functions during the injection cycle, to permittermination of the flow of the first polymer stream, then termination ofthe flow of the fourth and the third polymer streams, and thereaftertermination of the flow of the fifth and the second polymer streams, tothereby enable the apparatus to provide the parison with an inner layerformed from the third polymer stream that is continuous and completelyencapsulated within surface layers. (B) means for transferring theparison to a blow mold cavity, (C) means for inflating the parison inthe blow mold cavity to blow mold the parison into the finishedcontainer.
 10. The apparatus of claims 1,3,4,6,7,8, or 9 wherein themeans for coordinating permit the coordinated control and variation ofthe location and thickness of the respective streams relative to eachother and of the layers relative to each other in the parison.
 11. Theapparatus of claim 1 wherein the means for coordinating is also adaptedfor controlling and changing the thickness and location of the layer ofthe parison formed by the third polymer stream during the injectioncycle.
 12. The apparatus of claim 1 wherein said exit orifice for thethird polymer stream defines a thin polymer stream to form a thin innerlayer of said parison.
 13. The apparatus of claim 11 wherein said exitorifice for the third polymer stream defines a thin polymer stream toform a thin inner layer of said parison.
 14. The apparatus of claim 1wherein the means for coordinating the establishment, control andtermination of the three streams during each cycle, includes means forindependently terminating the first polymer stream forming the firstpolymer layer and for re-initiating the flow of said first polymerstream prior to terminating the flow of the polymer stream for formingthe outside surface layer of the parison.
 15. The apparatus of claim 3wherein the means for coordinating is also adapted for controlling andvarying the thickness and location of the layer of the parison formed bythe third polymer stream during the injection cycle.
 16. The apparatusof claim 3 wherein said exit orifice for the third polymer streamdefines a thin polymer stream to form a thin inner layer of saidparison.
 17. The apparatus of claim 15 wherein said exit orifice for thethird polymer stream defines a thin polymer stream to form a thin innerlayer of said parison.
 18. The apparatus of claim 3 wherein the meansfor coordinating the establishment, control and termination of the threestreams during each cycle, includes means for independently terminatingthe first polymer stream forming the first polymer layer and forre-initiative the flow of said first polymer stream prior to terminatingthe flow of the polymer stream for forming the outside surface layer ofthe parison.